Electric discharge tube of the kind comprising an indirectly heated cathode



April 22, 1952 H. J. DE WEYER ELECTRIC DISCHARGE TUBE OF THE KINDCOMPRISING AN INDIRECTLY HEATED CATHODE Filed Feb. 17, 1949 J /1/ /lnl//ll/1/A/4/4 /l/A /l/ /f /v////////// I//// /l fA 41m/EMM.

HENRICUS JOHAQINES DE WEYER 4 .U BY w 7AGENT Patented Apr. 22, 1952 lELECTRIC DISCHARGE TUBE 0F THE KIND -ooMPRIs1NG AN INDIRECTLY HEATED,oA'rHoDE Henricus Johannes de Weyer, Eindhoven, Netherlands, assignortoHartford National Bank and Trust Company, Hartford, Conn., as trusteeApplication February 17, 1949, SerialNo. 76,884 In the Netherlands March15, 1948 4 Claims. (CL 313-331) The invention relates Vto an electricdischarge tube having a cathode of the indirectly heated type comprisinga cylindrical sheath in which one or more heating wires are housed andin which the space between the sheath and the heating wires, at leastadjacent the ends of the cathode, is fully lled with insulatingmaterial.

It hasbeen found that the ends of the heating wires which emerge fromthe insulating material at the ends of the cathode frequently break offat thearea where the said heating wires emerge from the insulatingmaterial, on being bent to connect them to the supply conductors. Sincewe are always here concerned with comparatively thin heating wires whichby themselves may-be readily bent, this phenomenon could not be foreseenThe phenomenon is particularly inconvenient withcathodes of theindirectly heated type produced by mechanical operation, such asswaging,

rolling and drawing of a complex conductor, the. space between theconductors being consequently filled with strongly compressedpulverulent insulating material. Although the heating wires for suchcathodes may be very thin, so that bending thereof should prove topresent no diiculty, the said phenomenon is found to occur to an evenmarked extent.

The diiliculty may be obviated, if, in accordance with the invention,with an electric discharge tube comprising a cathode, of the indirectlyheated type which comprises a cylindrical sheath in which one or moreheating wires are provided and in which the space between sheath andheating wires, at least adjacent the ends of the cathode, is completelylled with insulating material, 5

the ends of the heating wires'which ends protrude from the insulatingmaterial, are iiattened, at least in part, starting at a slight distancefrom the point at which these ends protrude from the insulatingmaterial.

The flattened part as distinct from the remaining part of the heatingwire, is found to have greater exibility such that that part of theheating wires which protrudes direct from the insulating material is nolonger bent out of shape and breakage is avoided. An explanation is thatthe material of the heating Wires which, as a rule, is comparativelybrittle, may, in addition, become less brittle due to the flatteningoperation. Whatever the explanation oi the effect of the embodiment ofthe invention may be the result proves to be efficacious.

It is known to construct supply conductors outside the tube as rigidcontact pins and inside the tube as exible strips, the union betweenrigid :pin and ilexible strip being, for example. inthe seal. However,in the latter case, if thin wires were concerned, the phenomenonrequired to be v'avoided by the invention is liable to occur even withthis known construction. However, owing to the thickness of theconductors, in this known construction cracking of the glass is morelikely to occur than breakage of the conductors. Moreover, the materialof such supply conductorslis not so brittle as that of thin heatingwires. for cathodes. It is furthermore known to provide a grid stay Wirewith a thin flexible connecting wire. Also in this case the aboveproblem does not arise.

In order that the invention may be more clearly .understood and readilycarried into effect, it will now be described more fully with referenceto the accompanying drawing, in which:

Fig. 1 shows a tube and Figs. 2, 3 and 4 are detail views of cathodesaccording to the invention.

Referring to Fig. 1, I designates the bulb of a tube, which is sealed bya bottom 2 in which contact pins 3 are sealed.

Arranged in the tube is an electrode system 4 comprising a bifurcatedcathode 5 of the indirectly heated type constituted by a sheath 6 whichis coated with emissive material and which forms an equipotential body(Fig. 2). The sheath 6 contains insulating material 'I and a heatingwire 8 which is flattened at the end at 9. As is shown in Fig. 2, theflattened part 9 begins at a slight distance from the point at which theheating wire emerges from the insulating material, so that there isstill a non-deformed part I0. Gwing to the great exibility of part 9,part IB does not bend, so that rupture at the area at which the wireemerges from the insulating material is prevented.

In order to assist in welding the ilattened end to a vertical supplyconductor, this end may be torsioned as is shown in Figs. 1 and 2.However, in this case it is also possible to flatten the end of theheating wire for part of its length only and to leave the end II (Fig.3) undeformed or several flattened parts (Fig. 4) may be provided, theheating wire end being flattened at several areas in various directions,so that it is adapted to be flexibly bent in all directions without thepart II) being bent out of shape. Referring to-Fig. 4, parts 9 and I3are ilattened in directions at right angles to one another, whereas partI2 may4 remain undeformed.

1t is obvious that even other embodiments of the invention are possible.

- 3 What I claim is: 1. An electron discharge tube comprising anenvelope having a bulb portion and a base portion, an electrodestructure including an indirectly heated cathode,b`ody'mounted in saidbulb portion, an'outerconductive sheath on said cathode body, a .thinflexible heating wire in said sheath, and having an end portionextending out of said sheath at an extremity thereof, and amass-ofcompressed pulverulent insulatin'gjmaterial.llingf the space betweensaid heating wire and said sheath at said extremity, a supply .conductorpositioned on said base portion, said* thin;Y flexible:

heating wire having a iexiblecflattened portion electrically connectingsaid supply conductor and the said extended end portionof. said thin.ilexible heating wire.

2. An electron discharge tube comprising, an

blegflattene'd end portions at opposing endstherevoijelectricallyconnecting each oisaid supply conductors andvone ofsaid extended end portions of saidthn ilexible heating Wire.

, 3,;,Ajnj electron' discharge tube comprising` an envelopieshvn'gra'bulb portion and abase portion, an electrode structurezincluding anindirectlly heated'V cathode body mounted in said bulb portion said bodyhavingV a substantially U shape,

an' outer conductive'sheathon said cathode body,

agthin flexible heating'wire'in said'sheath and having opposingV endportions extending out of said sheath at opposite extremities of'saidsheath,

a. massoicompressed pulverulent insulating material lling the spacesbetween said heating `wire and said sheath at each said extremity, andsupply conductors positioned on said base portion, said thin iiexibleheating Wire having Iiexible attened end portions .at opposing endsthereof lelectrically connecting each' of saidsupply veonducztors andone of said extended end portions of said thin flexible heating wire.

4-.- An. electron discharge tube comprising an envelope.- having an bulbportion and a base portion, an electrode-,structure including anindirectly heated .Cathode body mounted in said bulb portionan outer;conductive sheath on said cathode body, a' heatinglwire in said sheathand having an end thereof extending out. of said sheath at an..extremity thereof, a mass .of compressed pulverulent insulating materialfilling the spacebetweensaid heating Wire and said sheath at saidextremity, a supply conductor positioned on said base portion, a firstflexible flattened member integral with said heating wire adjacent thesaid extended yend ofsa'id heating Wire; anda second iiexible flattenedmember integral with said heating wirefand electrically connectedlwithandextending at substantially right angles to' said-first attened memberandinterposed between said first member and said supply conductor.

HENRICUS yJOHANNES DE WEYER.

REFERENCES CITED The followingY references are of record in the file ofthis patent:

UNITED STATESPATENTS Number Name Datel Re. 19,870 Lederer et al. Feb.25,1935 247,097 Nichols'et al.' Sept.,13, 1881 1,914,883` CottrellJune20, 1933 1,968,280 Brian JulyBl, 1934 2,075,876 Von Wedel Apr. 6,1937 2,399,402 Herzog June'lS, 1944 2,403,444 Hartman July- 9, 1.946`2,403,4451 Liaco JulyV 9, 1946

